I had actually thought that printing concrete molds for the LR2 Y plates might be interesting, or patterns for aluminum casting.
The problem with casting MPCNC is that it has flex built into the design. The rollers for example need to flex outward slightly to hold the tube with the appropriate pressure. It has some ability to accommodate small errors in tube size, which also permits small errors in printing. The deflection ends up with some variation in squeezing pressure on the tube if the tube or printed parts are a bit off, but as long as it’s within a certain range, everything works.
Concrete or aluminum or other harder material would not flex the same and the existing design would not work. It would have to be remade with a significantly different design, perhaps with multiple hinged parts and springs or something.